The present invention relates to a substrate having a conductor path of solderable material arranged thereon and having a solder layer applied to the conductor path by contact as the conductor path moves along molten solder material.
Such substrates are known. Upon the application of the solder layer the conductor path is moved along the molten solder material and comes into contact with it. The solder material remains adhering to the conductor path. In particular, if the conductor path is moved transverse to its longitudinal direction along the molten solder material, the adherence of the solder material has the result that the solder material already applied to the conductor path remains for a moment connected to the solder material to be applied, even after the conductor path has already been moved away from this solder material. Only when a given distance away has been reached is this connection torn apart. As a result, a part of the solder material forming the connection is pulled back onto the conductor path which has been already provided with a layer of solder. As a result, however, the conductor path receives an excessively thick layer of solder.
In the case of a plurality of conductor paths some of which extend in the direction of movement of the substrate which moves past the solder material and the others transverse to said direction of movement the effect described above leads to substantially thicker layers of solder in the case of the transversely extending conductor paths than in the case of the longitudinally extending conductor paths.
The thickness of the layer of solder is also dependent on the width of the conductor path. This is due to the fact that in the case of wide conductor paths the layer of solder assumes a curved cross sectional shape and is thus substantially higher at the center than at the edge.
If the wide conductor paths are to be used as connections for insert-type contacts, the insert contacts slide off the curved conductor path even upon only slight vibration.
Another disadvantage of the larger solder cross sections is that due to the contraction in volume of the solder layer upon passage from the liquid to the solid state, this contraction amounting to about 9%, excessive stresses are produced between the conductor path coated with the solder and the substrate. In the case of a glass substrate with wide conductor paths as insert contacts in the region of its edge, this frequently leads to a crumbling of the glass.